The formation of the chemical synapse requires that both pre- and postsynaptic cells undergo a local specialization at the site of contact between the two cells. This process involves the concentration of synaptic proteins at the site and their assembly into a macromolecular complex that spans the synapse. The process is orchestrated by a series of signals that are exchanged between the two cells as synaptogenesis proceeds. Our laboratory is engaged in trying to understand what these signals are and how they act to drive the formation of the complex synaptic structures. We are interested in defining the components of the structure and how it is assembled. These studies are important for understanding how synapses function and how they are formed. Because important aspects of mental illness are thought to be mediated by changes in synaptic structure and function, these studies are highly relevant to understanding the biological basis of mental illness.